we have an exchange 2013 with say mydomain.local and then mydomain.co.uk and then another accepted domain mydomain2.co.uk.
The emails are flowing fine coming in.
One of the user has email set to mydomain2.co.uk as his primary and it can send and receive ok. The mydomain.co.uk email also exists for that user in the same mailbox.
In outlook 2013, he gets an option to choose which domain he wants to send email from ie. mydomain.co.uk or mydomain2.co.uk, by default, it is mydomain2.co.uk (accepted domain) as this is what is set in his default reply address.
When he choose to send from mydomain.co.uk, he gets a NDR straight away. Advice please?